Convection heater for fluids

ABSTRACT

A fuel and air mixture is supplied to a primary combustion chamber communicating with a secondary combustion chamber supplied with additional air to efficiently burn the fuel and elevate the temperature of the burned gases. The secondary combustion chamber communicates with a convector section containing tubing entrained therethrough in a tortuous path through which a liquid to be heated is circulated. A vent, connected with the convector section, discharges the exhaust gases.

United States Patent [1 1 Smalling Jan. 21, 1975 CONVECTION HEATER FOR FLUIDS 3,266,725 8/l966 Garrison et al. 236/15 B [76] Inventor: Charles E. Smalling, 7994 Locke Lee, Houston, Primary Examiner-Carroll B. Dority, Jr.

[22] Filed: Aug. 6, 1973 [57] ABSTRACT PP N05 386,267 A fuel and air mixture is supplied to a primary com- I bustion chamber communicating with a secondary [52 us. or. 431/80, 236/15 B COmbUStiO" chamber PP with additional air [51 Int. Cl. F23n 5/10 efficiently bum the fuel and elevate the temperature [58] Field of Search 431/75, 78 236/15 B of the burned gases. The secondary combustion chamber communicates with a convector section containing 56 R f d tubing entrained therethrough in a tortuous path 1 UNITE]; 5.22 .33 QZ through'which a liquid to be heated is circulated. A 2 420 999 5/947 A 431/190 vent, connected with the convector section, discharges yers 2,991,332 7/196l Dailey 236/15 B the exhaust gases 3,057,707 l0/l962 Braconier et al. 43l/8O 1 Claim, 6 Drawing Figures PATENTEI] JAN 2 1 I975 SHEET 10F 2 CONVECTION HEATER FOR FLUIDS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to heaters and more particularly to a convection heat transfer apparatus for elevating the temperature of a fluid circulating through a series of coils interposed in the burned gas exhaust stream.

2. Description of the Prior Art Prior patents generally disclose upright heat transfer apparatus for convection heating of a fluid flowing through a bank of tubing interposed in the burned gas SUMMARY OF THE INVENTION A generally cylindrically horizontally disposed primary combustion chamber is supplied with fuel mixed with a forced draft of air. The primary combustion chamber communicates with a cylindrical secondary combustion chamber supplied with an additional forced draft of air for complete burning of the fuel mixture and elevating the temperature of the burned gases with the secondary combustion chamber communicating with an enlarged convector section having a fluid conducting bank of tubing entrained therethrough. The temperature of the burned gases and quantity of fuel is controlled by a thermostat heat sensing means maintaining the burned gases at a desired temperature by regulating the fuel and air entering the primary combustion chamber.

The principle object of this invention is to control the temperature of heated gases from a burning fuel mixture applied to a convection heat transfer apparatus for heating fluid circulated through piping entrained in the heated gas stream.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of the apparatus; FIG. 2 is a top view of FIG. 1; FIG. 3 is a fragmentary vertical cross-sectional view taken substantially along the line 33 of FIG. 1; FIG. 4 is a fragmentary vertical cross-sectional view taken substantially along the line 44 of FIG. 2;

FIG. 5 is a left end elevational view of FIG. 4; and, FIG. 6 is a flow diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENT Like characters of reference designate like parts in those figures of the drawings in which they occur.

In the drawings:

The reference numeral 10 indicates the apparatus, as a whole, comprising a primary combustion chamber I2. a secondary combustion chamber 14 in turn connected with a convector section 16 by a transition section 18 with a burned gas exhaust 20 connected with the outlet end of the convector section. Control means,

indicated at 22, supplies a combustible fuel and air mixture to the primary combustion chamber 12 in the manner hereinafter explained.

The primary combustion chamber 12 includes a fuel and air mixing chamber 24, at one end thereof. having a fuel supply connection or tee 26 and an air supply tube 28 connected thereto. The fuel supply tee 26 is coaxially connected to the fuel mixing chamber 24 with a spark igniter or glow plug 30 connected to the wall of the mixing chamber 24 adjacent the inlet end of the tee 26. The air supply tube 28 is tangential with the wall forming the mixing chamber 24 to induce rotary motion and thorough mixing of the fuel and air. The air is supplied by a primary blower 32 connected by tubing 34 to the air supply tube 28. Piping 36 connects a supply of fuel, such as gas, to the fuel mixing chamber connected tee 26. Air-gas volume flow control means, comprising interconnected pneumatic valves 38 and 40 operate together to supply fuel and air to the fuel mixing chamber 24. A substantially funnel-shaped conductor 42 is coaxially disposed within the fuel mixing chamber 24 with its smaller end opening into the primary combustion chamber 12. The primary combustion chamber 12 is provided with a surrounding metallic outer wall 44 having a layer of refractory material 46 adjacent its inner surface. An inner wall of other refractory material, such as firebrick 48, forms an inner lining for the primary combustion chamber 12 which also shields the converging end portion of the funnelshaped conductor 42.

The secondary combustion chamber 14 is coaxially connected to the end of the primary combustion chamber opposite the fuel mixing chamber 24. The secondary combustion chamber 14 is provided with a surrounding metallic or jacket wall 50 and includes an inner wall formed of refractory material 52 in inwardly spaced relation with respect to the inner surface of the outer wall 50 with this spacing filled with a heat insulating material 54. A secondary air supply or blower 56, driven by a motor 58, is mounted on support brackets 60 above and to one side of the secondary combustion chamber 14 with respect to its longitudinal axis. The air exhaust tube 62, of the secondary blower, is connected to the secondary combustion chamber 14 substantially tangential to the periphery of the secondary combustion chamber by an adaptor 64 secured to the wall of the secondary combustion chamber around an opening 66 extending along an arc of its periphery so that air exhausted by the secondary blower generates a flow of the air and partially burned gases entering the secondary combustion chamber in a direction opposite to the angular direction of rotation imparted to the fuel and air entering the fuel mixing chamber 24. The adaptor 64 is similarly provided with an outer metallic wall 68 lined with a layer of refractory material 70 integrally joined with the refractory material 42 within the secondary combustion chamber. The air exhaust tube 62 of the secondary blower is provided with a substantially conventional damper for controlling the volume of air induced into the secondary chamber.

The transition section 18 is substantially trapezoidshaped in plan view with one of its parallel edges coaxially connected to the outlet end of the secondary combustion chamber 14 and its other end connected to the convector section 16. The convector section 16 is substantially rectangular in general configuration and is provided with inlet and outlet openings 72 and 74, re-

spectively, which receives pipe or tubing 76 entrained in a tortuous path throughout the interior of the convector section, such as is illustrated by the arrows 78 (FIG. 6). The piping 76 is preferably of the type provided with helically connected fins to increase its convection heating properties for fluid contained by the tubing. A burned gas exhaust stack 80 is preferably connected with the vent fitting 20.

A manual off-on valve 82, in the gas supply line 36, controls fuel to the burners. A regulator 84 is interposed in the fuel line between the off-on valve 82 and pneumatic valve 38 with a manual trip release valve 86 interposed in the fuel line 36 between the regulator 84 and pneumatic valve 38. A pilot gas supply line 88 is connected with the fuel line 36 between the regulator and trip release valve and connected at its other end with the fuel supply 26. A solenoid valve 90, interposed in the pilot supply line 88, controls the gas flow through the pilot supply line in combination with a needle valve 92 interposed in the pilot supply line between the solenoid valve 90 and the fuel supply fitting 26. A thermocouple 94 is connected with the wall of the transition section 18 and to a solenoid valve 96 through a temperature responsive thermostatic control 98. The solenoid valve 96 is connected with a supply of air under greater than atmospheric pressure by a line 100 with an air pressure regulator 102 interposed in the line 100. A solenoid valve 104 is interposed in the air supply line 100 between the regulator 102 and thermal actuated solenoid valve 96. The thermal actuated solenoid valve 96 is connected to the pneumatic valve 38 by a line 106 through a second needle valve 108.

OPERATION The components are assembled as described hereinabove and when initially placed in operation the control valve 82 is manually opened supplying fuel through the pilot supply line 88 to provide a pilot flame within the fuel mixing chamber 24 by means of the energized glow plug 30. The pneumatic valve 38 and primary air supply valve 40 are normally open. The trip release valve 86 is actuated to permit fuel to flow through the fuel line 36 while simultaneously the primary blower 32 has its motor energized to supply additional air to the fuel mixing chamber 24. The burning fuel, under forced draft, as a result of fuel pressure and primary air from the primary blower 32, enters and partially burns in the primary combustion chamber 12 while moving downstream into the secondary combustion chamber 14 where additional air supplied by the secondary combustion blower 56 thoroughly mixes the burning gases by inducing rotation thereof in an opposite direction to that imparted to the gases by the primary blower 32. The burned gases heat the fluid contained by the piping 76 by a scrubbing action within the convector section 16. In the event the burning gases temperature varies a predetermined number of degrees beyond a predetermined temperature according to the setting of the thermocouple 94, the thermostatic control actuates the solenoid valve 96 which appies or releases air under pressure to or from the pneumatic valve 38 to partially close or open this valve and simultaneously similarly operating the air supply valve 40 to reduce or increase the quantity of fuel mixture entering the primary combustion chamber 12. In actual practice, when the temperature within the transition section 18 increases beyond a desired temperature, the thermostatic valve 98 opens the solenoid valve 96 to apply air pressure to the pneumatic valve 38 for partially closing the latter and the primary air supply valve 40 to reduce the quantity of fuel mixture entering the primary combustion chamber 12 and as a result decreasing the volume of burning gases entering the secondary chamber 14 thus reducing the temperature of the heated gases to a desired level as they are conveyed to the convection chamber 60.

Obviously the invention is susceptible to changes or alterations without defeating its practicability. therefore, I do not wish to be confined to the preferred embodiment shown in the drawings and described herein.

1 claim:

1. A convection heater for fluids, comprising:

an elongated horizontally disposed housing having an inlet end portion and an outlet end portion forming a heated gases passageway therebetween,

the inlet end portion of said housing forming a primary combustion chamber and a secondary combustion chamber,

the outlet end portion of said housing forming a convection chamber communicating with the secondary combustion chamber;

said housing having a lateral opening in its area forming the secondary combustion chamber;

fuel mixture supply means including supply pipe means coaxially connecting a source of fuel to the inlet end of the primary combustion chamber,

a primary blower having an outlet,

tubing connected at one end with the outlet of said primary blower and connected at its other end with the fuel mixture supply means in tangential relation with respect to the axial direction of flow of fuel entering the primary combustion chamber, and,

a pressure operated volume flow control valve interposed in said supply pipe and said tubing, respectively,

said control valves being interconnected for opening and closing in unision;

means igniting said fuel mixture;

means supplying a forced draft of oxygen to the burning fuel mixture within the secondary combustion chamber including a secondary blower having an outlet opening coaxially connected with the lateral openings of said housing; and,

control means responsive to the temperature of heated gases adjacent the downstream end of the secondary combustion chamber for regulating the quantity of fuel mixture entering the combustion chambers and the temperature of heated gases flowing through the convection chamber,

, said control means including,

piping operatively connecting a source of fluid under greater than atmospheric pressure with at least one of said volume flow valves for opening and closing the latter,

a solenoid valve interposed in said piping,

a thermocouple connected with said housing between the secondary combustion chamber and the convection chamber, and,

means including a temperature responsive thermostatic control interposed between and connected with said thermocouple and said solenoid valve for opening and closing said solenoid valve and applying fluid pressure to said one volume flow valve for opening and closing said one volume flow valve in response to decrease and increase, respectively, beyond a predetermined range of the temperature of burning gases leaving the secondary combustion chamber. 

1. A convection heater for fluids, comprising: an elongated horizontally disposed housing having an inlet end portion and an outlet end portion forming a heated gases passageway therebetween, the inlet end portion of said housing forming a primary combustion chamber and a secondary combustion chamber, the outlet end portion of said housing forming a convection chamber communicating with the secondary combustion chamber; said housing Having a lateral opening in its area forming the secondary combustion chamber; fuel mixture supply means including supply pipe means coaxially connecting a source of fuel to the inlet end of the primary combustion chamber, a primary blower having an outlet, tubing connected at one end with the outlet of said primary blower and connected at its other end with the fuel mixture supply means in tangential relation with respect to the axial direction of flow of fuel entering the primary combustion chamber, and, a pressure operated volume flow control valve interposed in said supply pipe and said tubing, respectively, said control valves being interconnected for opening and closing in unision; means igniting said fuel mixture; means supplying a forced draft of oxygen to the burning fuel mixture within the secondary combustion chamber including a secondary blower having an outlet opening coaxially connected with the lateral openings of said housing; and, control means responsive to the temperature of heated gases adjacent the downstream end of the secondary combustion chamber for regulating the quantity of fuel mixture entering the combustion chambers and the temperature of heated gases flowing through the convection chamber, said control means including, piping operatively connecting a source of fluid under greater than atmospheric pressure with at least one of said volume flow valves for opening and closing the latter, a solenoid valve interposed in said piping, a thermocouple connected with said housing between the secondary combustion chamber and the convection chamber, and, means including a temperature responsive thermostatic control interposed between and connected with said thermocouple and said solenoid valve for opening and closing said solenoid valve and applying fluid pressure to said one volume flow valve for opening and closing said one volume flow valve in response to decrease and increase, respectively, beyond a predetermined range of the temperature of burning gases leaving the secondary combustion chamber. 